// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CC_BASE_DELAYED_UNIQUE_NOTIFIER_H_
#define CC_BASE_DELAYED_UNIQUE_NOTIFIER_H_

#include "base/callback.h"
#include "base/macros.h"
#include "base/memory/weak_ptr.h"
#include "cc/base/cc_export.h"

namespace base {
class SequencedTaskRunner;
} // namespace base

namespace cc {

class CC_EXPORT DelayedUniqueNotifier {
public:
    // Configure this notifier to issue the |closure| notification in |delay| time
    // from Schedule() call.
    DelayedUniqueNotifier(base::SequencedTaskRunner* task_runner,
        const base::Closure& closure,
        const base::TimeDelta& delay);

    // Destroying the notifier will ensure that no further notifications will
    // happen from this class.
    virtual ~DelayedUniqueNotifier();

    // Schedule a notification to be run. If another notification is already
    // pending, then it will happen in (at least) given delay from now. That is,
    // if delay is 16ms and a notification has been scheduled 10ms ago (ie, it
    // should trigger in no less than 6ms), then calling schedule will ensure that
    // the only notification that arrives will happen in (at least) 16ms from now.
    void Schedule();

    // Cancel any previously scheduled runs.
    void Cancel();

    // Cancel previously scheduled runs and prevent any new runs from starting.
    // After calling this the DelayedUniqueNotifier will have no outstanding
    // WeakPtrs.
    void Shutdown();

    // Returns true if a notification is currently scheduled to run.
    bool HasPendingNotification() const;

    base::TimeDelta delay() const { return delay_; }

protected:
    // Virtual for testing.
    virtual base::TimeTicks Now() const;

private:
    void NotifyIfTime();

    base::SequencedTaskRunner* const task_runner_;
    const base::Closure closure_;
    const base::TimeDelta delay_;

    // Lock should be held before modifying |next_notification_time_| or
    // |notification_pending_|.
    mutable base::Lock lock_;
    base::TimeTicks next_notification_time_;
    bool notification_pending_;

    base::WeakPtrFactory<DelayedUniqueNotifier> weak_ptr_factory_;

    DISALLOW_COPY_AND_ASSIGN(DelayedUniqueNotifier);
};

} // namespace cc

#endif // CC_BASE_DELAYED_UNIQUE_NOTIFIER_H_
